Multiple split year cases

[hood]

Assume:
Individual files a 2018/19 return stating that split-year Case 1 and Case 3 both apply.
In 2019/20 the individual fails to meet the 3rd automatic overseas test (due to either a gap in overseas employment or working more than 30 days in the UK).
Thus the 2018/19 Case 1 claim is no longer valid, since Case 1 requires 3rd automatic overseas test the following year.

However, the individual is still UK non-resident in 2019/20 based on the sufficient ties test.

Question 1: does the the 2018/19 split year claim remain valid due to Case 3?
Question 2: does the individual need to file an amended 2018/19 return removing Case 1 and stating that only Case 3 applied?

thanks in advance

[maths]

Presumably Box 3.1 of SA 109 was completed by inserting "X" and information was provided in Box 40 referring to Cases 1 and 3.

Where Cases 1 and 3 are both satisfied, Case 1 takes precedence.

In the absence of further information or questions from HMRC, HMRC will operate on the basis Case 1 applies (not Case 3). It would then seem the taxpayer is at risk from Discovery with the attendant consequences.

It would therefore seem necessary for an amended Tax Return to be filed.